I. Field of the Invention
The present invention relates to a high-performance composite thermally insulating material comprising a composite of a vacuum thermally insulating material and an ordinary thermally insulating material used, for example, in houses.
II. Description of Related Art
In houses and the like, for the purposes of enhancing the thermal insulation properties of the walls and roof, etc, the usual means employed is either to increase the thickness of the fitted thermally insulating materials or to select a thermally insulating material of still lower thermal conductivity, that is to say better heat insulating performance. However, in the case of the insulation of the walls of houses for example, since the thermally insulating material is used to fill the restricted cavity between the outer and inner walls, there is a limit to the enhancement of the heat insulating performance by increasing the thickness of the thermally insulating material.
Furthermore, with regard to thermally insulating materials with good heat insulating performance, amongst those thermally insulating materials currently employed, in the case of plastic thermally insulating materials it is possible to achieve a level of heat insulation of about 0.02 W/m·K. However, this value is essentially the limit and, in particular, it is insufficient for use in buildings in cold or very hot regions. Hence, in addition to filling the wall cavities with an insulating material, it is necessary to add heat-insulating cladding.
The vacuum thermally insulating materials described in Japanese Patent 3580315 (JP2005220954), WO0185445 or Japanese Patent 3578172 (JP2005180594) are known as high-performance heat insulating materials in other fields. In the case of such vacuum thermally insulating materials, a core material like glass wool is packed inside an outer covering material comprising a plastic film or the like, and by maintaining a vacuum in the core region it is possible to exhibit high thermal insulation. Such materials are used primarily for thermal insulation in freezers and refrigerators, etc.
Vacuum thermally insulating materials have high performance but they are very weak in terms of external impact. Consequently, if the vacuum thermally insulating materials disclosed in aforesaid references were to be converted to use in houses, when subject to impact during transportation or fitment, etc, cracks and pinholes would readily be introduced and the interior vacuum impaired. Moreover, once the degree of vacuum is lowered, the performance drops immediately to that of an ordinary fibre-based thermally insulating material. Consequently, they are difficult to employ for house insulation.